For example, in an eye fundus camera that photographs patient's eye fundus image in the checkup or the ophthalmologic examination, a photographing function in a high dynamic range is desired to stably acquire an eye fundus image of high quality.
In an eye fundus image assuming person's eye fundus as an object, the reflection of a light source is strong and blown-out highlights are likely to be caused in an optic disk region from which retinal nerves come out in a bundled manner, and the reflection intensity is weak and therefore blocked-up shadows are likely to be caused in a macular region corresponding to the central fovea.
To perform photographing so as not to cause the blown-out highlights in the optic disk region, the exposure setting at the time of the photographing has to be optimized and the photographer's skill is demanded. Moreover, even if photographing is performed so as not to cause the blown-out highlights in the optic disk region, the macular region and the peripheral region may be filled with black and become difficult to be diagnosed. In view of such state, a photographing function in a high dynamic range is desired for an eye fundus camera.
Therefore, as a technique to acquire an eye fundus image of a high dynamic range, there is suggested a method of defining the suitable light quantity in each region on the basis of the first photographing result (for example, see JP 2011-31027 A).
In this method, first, the light quantities of the optic disk region and the periphery are acquired by the first photographing, and, in the second photographing, photographing is performed by a suitable light quantity with respect to an area of the optic disk region which is defined by the first photographing and the area of the optic disk region is extracted from an acquired image.
Further, in the third photographing, photographing is performed by a suitable light quantity with respect to a peripheral area near the optic disk region which is defined by the first photographing, and the peripheral area is extracted from an acquired image. Moreover, the area of the optic disk region and the peripheral area which are acquired as above are synthesized to acquire one eye fundus image of a high dynamic range.